It is the common practice in the manufacture of insulation materials to carry the insulation on an endless belt, to compress the insulation to a fraction of its former volume, and to deliver the compressed insulation to a packaging machine which can roll up or otherwise package the insulation material. The apparatus used to compress the insulation material in existing applications generally comprises a compression member positioned above the transport conveyor to force the insulation material through a progressively decreasing opening in order for the compression to take place. Typical compression ratios between the initial thickness of the insulation material and the compressed thickness of the insulation material are about 5 to 1, or higher.
One of the problems associated with packaging such compressible material is that frequently the compressed material contains a significant amount of compressed air. The presence of compressed air is the result of the insulation material traveling past the compression member at a rate exceeding the rate at which air can escape during compression. The problem has been magnified by two technological advances of recent years: line speeds have increased significantly, and today's wider and thicker insulation packs prevent a sufficient amount of air from escaping through the sides of the pack. This is in contrast to previous packaging operations for narrower insulation packs.
Compression of insulation packs without permitting escape of the air results in a compressed pack which will expand due to the expansion of compressed air as soon as the confinement is released. This usually necessitates a recompression of the pack in the packaging machine itself. Such recompression is undesirable since each compression cycle of insulation material weakens the material and adversely affects pack recovery. Also, some additional energy is required to recompress the insulation material in the packaging machine if air is not properly vented from the compressible material during the initial compression.
A potential problem is that the pack will travel through the compression apparatus at a rate sufficient to cause the pack to explode or burst out backwards from the entrance of the compression area. Another problem is that the air escapes sideways through the edges of the pack, thereby damaging the pack edges and distorting the pack out of shape.
Attempts have been made to solve the problem of excess compressed air during compression by providing transverse apertures or slits in the compression member for the escape of air. These proved to be inefficient, however, because the slits soon became clogged with loose fibers and binder. If the slits were made wide enough so that they did not clog, the insulation received a washboard treatment as it passed through the compression member, thereby damaging the pack surface.